In a cellular network mode, data traffic usually goes through centralized controller such as a base station (BS) even if the communicating parties are close to each other. Current cellular networks operate in this centralized mode, which is also termed cellular mode in this disclosure. One main benefit of the centralized operation is easy resource control and interference control. One potential drawback is less efficient resource utilization. A double amount of resources may be needed for a user equipment (UE) in a cellular mode. For example, a cellular UE may need to have a first radio resource allocated between the cellular UE and the base station and a second radio resource allocated between the base station and the other cellular UE. In comparison, a UE in a direct, device-to-device (D2D) mode may only need one radio resource between the UE and a pairing UE, when two users are sufficiently close to each other. Examples of the centralized controller may include NodeB (NB) of long-term evolution (LTE).
To help improve system throughput, a radio network may operate in a hybrid mode. In a hybrid mode, the UE may operate in the cellular mode if the other party is located far way and may operate in the D2D mode if the pairing UE is sufficiently close by. The hybrid mode operation is being explored in newer generations of network technologies such as 3rd generation partnership project (3GPP) long-term evolution advance (LTE-A) and worldwide interoperability for microwave access (WiMax) network. One example of D2D mode network is an ad-hoc network where one D2D UE may set up a direct connection with the pairing UE via a handshake and competition procedure. Examples of cellular networks include widely deployed networks such as universal mobile telecommunications system (UMTS) network, code division multiple access (CDMA) network, Wimax network and 3GPP LTE networks.